Self cleaning screen for placer mining machines



April 28, 1936. B. GOLDBERG ET AL SELF CLEANING SCREEN FOR PLACER MINING MACHINES Filed April 21, 1934 z/% QQQLJQQQ QQQQLJLJQU:

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. I I i I Patented Apr. 28, 1936 UNITED STATES SELF CLEANING SCREEN FOR PLACER 'MINING MACHINES Louis B. Goldberg, Nathan Goldberg, William Goldberg, and Jacob M. Goldberg, Denver,

Application April 21, 1934, Serial No. 721,742

1 Claim.

This invention relates to improvements in screening devices and has reference more particularly to a self-cleaning screen for use with placer mining machines.

In the recovery of gold from placer, gravel and sand, it is necessary to subject the placer material to a thorough scrubbing action in contact with water so as to separate from the gravel and gangue particles, the soils that contain the gold as these are nearly always quite closely attached to the gangue.

Since placer, gravel and sand is found in or near creeks or under surface that is covered with vegetable growth of different kinds, the placer l5 material is usually mixed with fibrous material, such as roots which have a tendency to clog the screen and it is therefore necessary to make some provision to maintain the screen in operative condition, regardless of such tendency to clog.

This invention, briefly described, comprises a supporting frame on which is mounted for rotation a, substantially cylindrical screen whose outer wall is provided with a large number of openings extending substantially parallel to the axis of rotation and which have the material of their edges offset in such a way that the edge that points in the direction in which the screen is rotating, is farther from the center of rotation than the opposite edge. 30 derneath it, a trough which is preferably curved about the center of rotation and which extends over at least 180 degrees of the lower surface thereof. This trough is provided at one end with an end wall that projects upwardly and serves to 35 prevent water from leaking out at the end nearest the intake of the screen. The distance from the outer surface of the screen to the inner surface of the drum is comparatively small so that the water that passes through the openings will be carried upwardly by the upwardly advancing surface of the screen and made to flow back into the drum through the openings, thereby setting up a local circulation between the interior of the drum and the contents of the trough.

Having thus briefly described the invention, the same will now be described in detail, and for this purpose reference will be had to the accompanying drawing in which the preferred embodiment thereof has been illustrated, and in which:

Fig. l is a side elevation of the improved screen;

Fig. 2 is a longitudinal section through the screen taken on a vertical plane;

Fig. 3 is a transverse section taken on line 3-3, Fig. 2; and

This screen has located un- Fig. 4 is a section of a portion of the machine taken through the discharge opening of the trough.

In the drawing reference numerals 5 indicate the vertical corner posts of a supporting frame that is provided on opposite sides with horizontal frame members 6, 1, and 8. Since the supporting frame can be constructed in any manner desired and has been indicated more or less diagrammatically, no detail description of the same will be given and only such parts thereof will be referred to as are necessary to properly describe the invention.

Frame members 1 are offset near one end and have a portion which has been designated by reference numeral 9 to which bearings ID are secured. Each hearing ID has rotatably mounted therein a roller H, there is one roller on each side, and these rollers are spaced so as to form a support for the cylindrical intake section I2 of the screen l3. Secured to each longitudinal frame member'l is a pair of bearings M in which is mounted for rotation a shaft I5. One end of the shaft has secured to it a roller i6 and the other a sprocket wheel ll to which a sprocket chain I8 is connected. The sprocket chain [8 preferably extends to a motor or internal combustion engine that provides the power for rotating the screen, but as this is a conventional arrangement, the motor has not been shown. The discharge end of the screen is formed by a short cylindrical section 19 to the outer surface of which an angle iron is secured. The angle iron 20 serves as a track for the rollers IS. A similar angle iron 2| is secured to the cylindrical portion l2. Supported from the frame members 8 is a semi-cylindrical trough 22 that extends substantially the full length of the screen section l3 and which is provided at its upper end with an end member 23 that has its upper edge provided with a semi-circular opening of the proper size to receive the cylindrical portion l2 as indicated in Fig. 2. The trough 22 has a discharge opening 24 at its lower end and is preferably provided with an arcuate end member 25 that serves as a stop for the material that flows down the trough when the screen is operating.

The screen section I3 is preferably formed. from a single sheet of steel which is provided with a plurality of slits that extend in the direction of the axis of rotation. The material on one side of each slit is bent inwardly as indicated by reference numeral 26 and the side that is not bent inwardly and which has been indicated by reference numeral 21 will therefore be farther from the center of rotation than the edge of the part marked 26, and when the screen is rotating in the direction of arrow 28, in Fig. 3, the edge 21 will point in the direction of rotation with the result that the contents of the screen, as the latter rotates, will be carried up to some extent on the upwardly moving surface and will then flow downwardly over the inner surface of the bent portion 26, thereby producing a cleaning action which has a tendency to remove from the openings any roots, grasses or other material that would otherwise clog the openings. Another action that is due to the specific construction of the screen and its relation to the stationary trough is that when the inside of the trough is spaced a comparatively short distance away from the outer surface of the screen, as, for example, two inches, the friction between the rotating screen and the water will cause the latter to move upwardly with the advancing side of the cylinder and downwardly with the downwardly moving side so that the water along the upwardly advancing side will reach the point designated by reference numeral 29 and the water on the downwardly moving side will be displaced to the point indicated by reference numeral 30. This difference in level, together with a suction caused by the flow of liquid down over the inclined surfaces 26, produces a circulation of water from the trough through the openings as indicated by arrow 3| in Fig. 3, and thence outwardly through the openings and into the trough. This local circulation of the pulp gives a very effective scrubbing and washing action that would not be at- J tained if the stationary trough were not present.

At the discharge end of the screen an inwardly extending flange 32 is provided, and between it and the cylindrical discharge opening l9 there is formed an annular channel 33, the bottom of which is provided with perforations 34 as shown in Fig. 2. The material, which consists of placer material and water, is introduced into the rotating screen through the hopper 35 and after it has passed through the screen it is discharged onto a trough 36 that conducts it away from the machine to the tailings dump.

The concentrates or fines that pass through the openings in the screen are discharged from the trough 22' through the opening 24 as indicated by arrow 31 and this material falls on a removable riflle 38 that moves in the direction of the arrow 39. As the rifile forms no part of this invention, it has merely been indicated diagrammatically and will not be described with any further particularity.

From the above description it will be apparent that by the combination illustrated on the drawing and described herein, danger of having the screens stop up whenever fibrous materials are present in the placer material is obviated to a great extent and in addition to this there is an increased scrubbing and washing action due to the recirculation of the pulp from the trough to the inside of the screen in the manner illustrated in Fig. 3.

Having described the invention what is claimed as new is:

A combined washing and screening device for use with placer mining machines comprising, in combination, a supporting frame, a substantially cylindrical screen carried by the frame and mounted for rotation about its longitudinal axis, one end of the screen cylinder having an intake opening of smaller diameter than the screen, and the other end having a discharge opening which is of a smaller diameter than the screen, the axis of the screen being inclined toward the discharge opening, the wall of the screen being formed from sheet metal and having a plurality of elongated openings extending in the direction of the axis of rotation, the material on opposite sides of the openings being offset in such a way that the edges on the advancing sides is farther away from the center of rotation than opposite edges so as to form scoops for directing water into the interior of the screen and whereby when the screen is rotated the movement of the material within the screen will effect a cleaning action, a stationary substantially semi-cylindrical trough located underneath the screen and surrounding the lower half thereof for receiving water from the screen and holding it against the outside thereof whereby the water will be carried upwardly by the upwardly moving surface of the screen and made to flow inwardly through the openings thereby dislodging any material that has become lodged in them and whereby a circulation of water is produced between the screen and the trough, a wall extending upwardly from the trough at the end near the feed opening in the screen to prevent water from flowing out of the trough at that end and a similar wall extending upwardly from the trough at the discharge end of the screen, the bottom of the trough having a discharge opening at the end nearest the discharge end of the screen.

LOUIS B. GOLDBERG. NATHAN GOLDBERG. WILLIAM GOLDBERG. JACOB M. GOLDBERG. 

